Large-scale structural parts, such as bridges, ships, high-speed rails, wind turbine blades, aircraft wings, are subjected to effects of adverse factors such as vibration, corrosion, hygrothermal aging, harsh environments and the like in long-term use, thus inevitably resulting in fatigue and damage accumulation; and in addition, some unexpected events, such as heavy collisions, flying stone and hail impacts, lightning strikes and the like would also cause damage accumulation and expansion of the structural parts. In most cases, such damage accumulation and expansion are invisible and unexpected, leaving a great potential safety hazard for use of the structural parts, and may even result in serious sudden accidents, causing irreversible losses. Based on the above problems, it is particularly important to perform online health monitoring on the structural parts in their service process.
Constrained by sensors, most of the health monitoring on the structural parts are based on offline nondestructive solutions such as X-ray, ultrasonic, infrared ray. Although a certain degree of active online monitoring can be achieved by externally pasting strain gages, inter-implanting strain lines and the like, but this type of sensors are fragile, corrodible, short in service life, and vulnerable to external force impact, electromagnetic interference. The online health monitoring on the large-scale structural parts needs a temperature and strain monitored sensor element with high sensitivity, good stability, high strength, long service life, aging resistance, anti-interference capability.
The fiber grating, serving as a sensing element sensitive to strain and temperature sensitivity, uses an optical signal as a measurement signal source, and has high electromagnetic interference resistance and high measurement accuracy, and a single optical fiber can realize the online measurement of strain and temperature of dozens of nodes. However, the essence of a fiber grating sensor is a small, brittle glass fiber with an engraved grating, and it is easily broken and inactivated during by external force the process of implanting or externally affixing on the structural part and during normal detection work.
At present, the fiber grating is generally packaged with metal or plastic materials, and the package process is complicated and costly; the metal has high density and is likely to be corroded, and the installation and maintenance are inconvenient. In addition, the compatibility of metal materials with composite materials is poor, and it is easy to form defects when implanted in a large-scale composite material structural part. Therefore, it is of great significance to prolong the service life of the sensor by producing a non-metallic and lightweight composite material packaged fiber grating sensor with high strength and corrosion resistance. In addition, if the composite material packaged fiber grating sensor can be pasted on the surface and implanted inside the structural part to achieve distributed online measurement of temperature and strain of both the surface and interior of the structural part, it is of great significance for the health monitoring on the structural part.